yamaha 9hp service

[rayiow]

Hi all,went out all night in my 12ft boat(powered by yam 9hp, 40 mins into journey (at full revs)engine slows then dies then i could smell evidence of a very hot engine.anchored up for afew hrs to fish(mate with me in his boat'few') then engine started ok and got back in under own steam(no pun intended lol)although kept revs under half and cowel off,a light spray of water seen coming out from base of engine(as it should) but i am thinking of replacing the impeller and also looking at the thermastat,what else should i look at because of the overheating!!? also above the prop and just above the cavitation plate are 2 screws 1 says OIL and the other one says WASH the one that says WASH is about 10mm below the oil one what is the WASH one for??.i think it is a 1970 9hp but that is all i can say i have placed a topic in to try and help me find out more about this engine so at the moment i cannot give you any more info about this engine sorry, any help/advice would be gratefull

 

[WillyBWright]

Re: yamaha 9hp service

The Flush is for connecting a garden hose via an adapter to flush the cooling system. This should be done after each use in saltwater, but is also useful for flushing out whatever the water pump may have sucked in. Most people use flushettes (muffs).<br /><br />There are two plugs for the gearcase. You drain and fill from the bottom plug until it comes out the upper plug.<br /><br />You might want to change your oil after that overheat. Heat breaks-down the oil somewhat. If you have fully synthetic oil in there, you probably don't have to worry about it. Synthetic tolerates heat and cold much better than petroleum.<br /><br />Your pump is still working, but may be weakened. I'm guessing you picked-up some weeds and some clogged the water intakes and restricted water coming in. You should at least check your water pump. As long as you have to take the gearcase off to do it, you might as well put in a new impeller regardless.

 

[rayiow]

Re: yamaha 9hp service

thanks for your info willybwright,impeller was fine(looks like new) but the thermastat was siezed with only a small gap(placed in hot water and no movement)would it be a problem if i do not replace the thermastat?. i also found that the pipe from the impeller up to the block was loose and leaking badly at the block end so i have yet got the enjoyment of getting to it mmmmmmm so hopefully these are what where making the engine overheat...thanks again.

 

[bossee]

Re: yamaha 9hp service

Hi,<br />My advice:<br />1. Buy a new thermostat.<br />2. Buy a new impeller kit unless You know the present status of the impeller, and rubber seals for the waterpipe (ends) between the impeller houseing and block. I assume it is rubber seals in both ends of the waterpipe.<br />3. Change oil in lower unit unless You have done it recently.<br /><br />This should get Your outboard in good shape again.<br /><br />Always a slight risk the carburator(s?) will need a rebuild sooner or later but lets hope later.<br /><br />Try to find the serialnr on Your Yamaha 9 hp and then make a new post in this forum and hopefully this way the year Your outboard was made can be determined.

 

[rayiow]

Re: yamaha 9hp service

Hi, thermostat now done just need to get access to base of block for rubber seals, but away for a couple of weeks it will have to wait but i am now itching to get it fixed, as for the serial number i have checked everywhere and the only numbers i have found are 65500/f1 which are on the engine,the id plate is missing just two corroded rivets mmmmmmm. the cowling says yamaha 9 yet i have never heard or seen another yam 9, 8hp yes but not 9's, anyway i got to go as i need sleep.

 

[rayiow]

Re: yamaha 9hp service

progress update... except for the block everything else stripped and all bolts came out without a struggle, thermastat replaced, top rubber from impeller into block replaced(old one was in bits), just got to rebuild it now. i have stripped various items of ally due to slight corrosion what is the best way to repaint the ally? do i have to use a etch primer!!, also just found out (by chance) that i cannot use copper ease on all my bolt threads!!.

 

[rodbolt]

Re: yamaha 9hp service

hello<br />retorque the head bolts or replace the head gasket,if it has a head. some of the early export motors did not use a head just had a water cover. cant help ya on the numbers.<br /> good luck and keep us posted.

 

[rayiow]

Re: yamaha 9hp service

just been to the yamaha dealer on the island(why did'nt i do this first i hear you say 'i did'nt realise there was one on the island!!!) to talk about what paint etc and by chance i had a tracing paper copy of the power head gasket(which i did last night to make own gasket) in the boot of car and with the numbers(65500) that i mentioned to him he said straight away yamaha 8B (it appears the wrong coweling is on the engine), very impressed with his service and knowledge(KEVIN MOLES 'isle o wight''GB'),I feel alot happier now but just got to paint and rebuild it. thanks again for your help

 

[rayiow]

Re: yamaha 9hp service

engine now painted and all cleaned and regreased, all back together now(phew) and works like a dream with a nice strong stream of water coming from the pee hole(big grin on my face now) although i had to re-adjust float in carb as on tickover fuel kept coming out. I have 2 red wires with bullet connectors beneath flywheel are these for lights or charging not too bothered as i probably won't use them(don't wanna fry the electric's now the engine is fine). thanks again for all your help i am such a happy chappy now lol.